Bearing



`Patented Dec. 15, 1936' BEARING charles n. short, clermont, F1a., -and Roxana P. Koehring, Dayton, Ohio, assignors, by mesne assignments, to General Motors Corporation,

Detroit, Mich., a corporation of Delaware Original application May 3, 1929, Serial No.

360,074, now Patent No. 1,939,467, dated December 12,1933. Divided and this application April 26, 1933, Serial No. 668,104

6 Claims.

Thisinvention relates to bearing elements having a bearing-metal lining and a reinforcing backing of a different metal, especially bearing elements having a bearing lining of porous bronze and a reinforcingbacking of ferrous metal, particularly heat treated steel.

This application is a division of our copending application Serial No. 360,074, iled May 3, 1929 now Patent No. 1,939,467, dated December 12, 0 1933.

Reference is made to Patent No. 1,768,528, granted June 24, 1930, and Patent No. 1,834,746, granted December. 1,- 1931, by Charles R. Short, wherein there is disclosed methods of making bearing elements by forming a relatively thin sheet of porous metal and attaching it to a steel or other metal backing by an intervening tin or other metal bonding-coating applied either to the lining 01 backing or both, al1 the metals being D bonded or alloyed together by heat.

It has been found that in these bearings under severe use there is a tendency for the bearing lining to become loose due to a loosening of the tin bond from the backing, or due to the rela- 5 tively low melting temperature of substantially pure tin, or one or more various other causes.

Now the present invention has for its object the overcoming of such bonding diiculties be` tween bearing linings and their metal backings,

, particularly to provide an improved method of securely and permanently bonding a bronze or other copper alloy part to a Aferrous metal part,

which bond will be .very strong at a relatively high temperature. In the methods described in the above mentioned patents, whenever-there is in the finished bearing a layer of free or unalloyed tin between the lining and backing, the maximum temperature at which such Ibearing can be run may be limited by the melting point of tin. The strength of the bond is'v of course greatly reduced as its temperature approaches the melting Apoint of tin. Now the present invention provides a bond between the ferrous metal and the bronze by the use of tin, but in such manner that inthe finished product the tin is so alloyed with rcopper that its melting point is raised above the maximum run- Y ning temperature of the bearing, which therefore may be above the melting point of tin. Briefly,

. this object may be accomplished by providing a very thin tin coating interposed' between -two metal surfaces both of which will alloy or diffuse into the tin (such as copper or copper alloy),

land heating, for a sirdicient time and at a sufiicient temperature to cause-the entire thickness of tin to be alloyed with metal from adjacent metal surfaces. Since copper will readily diffuse into pure tin below 1000 F. it has been found that the pure tin layer can be converted into a copper-tin alloy without raisingthe tempera r ture during this heat treatment beyond 1000 F., d or if need be, beyond 900 F. or lower.` Hence this invention is adapted tobond a bronze bearing lining directly to` a heat treated steel part without raising the temperature of the heat treated steel part to a point where the temper of the steel will be impaired.

l magniied from an actual distance apart of about For the purpose of illustrating this invention, it has been-described in connection with a connecting rod and cap bearing .of an internal combustion engine.

Further objects and advantages of the present invention will be apparent from the following description, reference being hadto the accompanying drawing, wherein a preferred embodiment of one form of the present invention is clearly shown.

In the drawing:

Fig. 1 represents a section through a heat treated steel connecting rod bearing assembled upon a bronze plug during the bonding step of 2" the illustrated process, the thickness of the bonding layer, however, being greatly exaggerated for the sake of clearness.

Fig. 2 represents a microscopic `view, magnied something like 1.25 times, of a section taken along line 2 2 of Fig. 1 prior to the heat treating or bonding step.

Fig. 3 is a .view similar to Fig. 2, but represents the'section after the bonding step is comp1eted. 3

In the embodiment illustrated the semi-cylin- A' drical porous bronze linings I0 are first made according to the above mentioned patents, or according to any other well known and suitable 40 methods. The preliminary forming of the linings Ill per se constitutes no part of this present in width and depth considerably, but Figs. Zand 3 illustrate the high ridges or lands 2li highly 1/64 of an inch. 'Ihe serrated steel surfaces l2. are first copper plated by-any suitable known method, preferably to a thickness of about .002 inch of Cu. In Fig. 2- this Cu'plating is designated by 2| and is represented as of substantially even thickness over the lands and grooves of the serrated steel surface. Next a very thin tin coating 22 is applied to the copper plating 2| by any suitable means which will give a minimum thickness of tin coating.v A suitable flux should be used before tinning, `'such as awater solution of zinc chloride which has been found satisfactory for this purpose. If the tinning is done by dipping, ali excess 'tin should be removed by some suitable method, such as by wiping off while hot with a rag or brush in a direction following the serrations. The tin coating 22 should completely cover the copper coating 2| and yetpreferably be ofthe minimum thickness possible. such for instance as .0002 inch. It has been found that the tin coating can be made extremely thin at the high areas, that is, on the summits of the lands 20, while in the grooves between the `lands it is somewhat thicker, as has been roughly illustrated in Fig. 2. y

Now having thus prepared the steel surfaces i2 with Cu and tin coatings, the tin surfaces are again iluxed with a suitable flux as, for example, a water solution of zinc chloride and the porous bronze linings I0 assembled thereupon and the rod and cap I3 then assembled upon a bronze plug |5 of the desired diameter by means of the bolts i6 and nuts I1 whichshould be drawn tight. There should be suillcient clearance between the meeting edges of the upper and lower steel parts as well as the linings I0 to insure that theclamping pressure will be all taken directly upon the. vbearing surfaces of the linings.r The bronze plug i5 having a greater coelcient expansion than steel, assures that pressure will be applied to the' joint to be bonded together all during the bonding heat treatment.

The bronze plug l5 should preferably be first coated with graphite and voil and baked to provide a coating thereon, or any other suitable method may be used which will prevent possibility of .plug I5 sticking to the porous bronze lining after the bonding heat treatment, and therefore permit readydisassembly of the parts.

The assembly, shown in Fig. 1, is next heated to such a temperature and for such a time as will cause some of the copper of the copper plating 2| and some ofthe copper in the porous bronze lining i0 to alloy or diffuse into 'the tin layer 22 to such an extent that substantially Vall the tin becomes alloyed with copper and its meltthe steel on its opposite side and hence the entire series of layers is bonded securely together. It has been found by microscopic examination that the tin coating is thinnest at the tops ofl the lands 20, and for this reason, presumably, theCu entering the tin layer from both sides thereof converts the tin layer into a bronze of higher copper content than obtains in the coppertin compound CuaSn at these high areas 25 (designated in Fig. l3V by the distance b)f These bronze areas .25 are strong and tough and provide the main physical bond between the lining i0 and the steel. Y

In the grooves, or low areas 26 (designated inat the lands l20, the diiusion of the copper through the tin layer is slower and the tin layer is or may be largely converted into the relatively hard and brittle CuaSn compound by the dii'- fusion into the tin of copper from both sides thereof. Such CuaSn compound has a suiiiciently high melting point to withstand the highest desired running temperatures for bearings and also aids greatly in the thermal bond between the porous bronze I0 and the steel back for rapid conduction of heat away from the bearing material. It has been found,'however, that the bond given by the tough bronze at the high areas 25 provides all the necessary physical `strength and the brittleness of the CuaSn in the low areas 26 is immaterial.

The above described bonding may be obtained by a heat treatment which will not impair the temper of the steel parts and i3. The pre-v below the desired bonding temperature and heat-v ing the container in a furnace for a period varying from 15 to 60 minutes at a maximum temperature which will not impair the temper of the steel parts, for instance, at 800 to 900 F. This method of heating in a closed container within a fiuxing atmosphere is morefully described and claimed in a prior application, Serial No. 333,014, filed Jan. 16, 1929, by Charles R. Short.

Of course, if desired, other suitable methods of heating to the desired temperature in a nonoxidizing atmosphere may be used, such for instance as dipping the assemblies of Fig. 1 in a molten lead bath maintained at the desired temperature. After removal from the lead bath, any lead which may adhere to the assembly can be easily removed with a wire brush while hot. i

In such bonding heat treatments, at the higher temperatures a more complete diffusion of the Cu into the tin occurs, while at the lower temperatures greater amounts of the brittle CuaSn remains. However, it has been found that the diffusion of the Cu into the tin can be increased with the length of time of heating, hence a. longer period of heating at a lower temperature corresponds to a shorter period at a higher temperature. steel or other heat treated parts to protect from the higher temperatures, the bonding heat treat-- ment of this inventionmay be carried out at temperatures much higher than 900 F., say up in 1400? F. and a saving of time of heating thus obtained.

The fundamental teachings of this invention are not limited to the use of bronze bearing linings, or a ferrous metal backing, or the use of any Therefore if there are nor heat treatedV particular metals 4for forming the bonding alloy or alloys. For instance, instead of forming the bonding alloy from copper and tin, as described above, it maybe formed from brass and tin, zinc and tin, cadmium and tin, copper and zinc, or other combinations of metals, by forming the metal coatings 2| and 22 accordingly. In each case there is formed a good bonding alloy intermediate the parts which are bonded together, having a higher melting point than that of its lowest lmelting component. If the bearing lining is of aluminum instead of bronze, as described above,

the coating 2| may be of copper with the coating 22 of zinc.

It is to be understood that this invention is not limited to thespecic examples disclosed hereinn Y ing surface and a separately made porous bronze bearing lining integrally bonded together over the high vareas of said finely roughened contacting surface by a non-brittle strata Whose entire thickness is composed of an alloy of copper and tin of higher copper content than obtains in the copper-tin compound CuaSn. y

3. A bearing element comprising a tempered steel backing and a separately made porous bronze bearing lining, said steell and bronze being integrally bonded together over a large number of small high areas by a strata whose entire thickness is composed of a copper tin alloy having a higher copper content than obtains in CuaSn. y

is composed of copper-tin alloy 4. A bearing element comprising a tempered steel backing and a separately made porous bronze bearing lining, said steel and bronze being bonded together by a copper plating upon the steel 'and a strata whose entire thickness is composed of 5 copper-tin alloy of high copper content between the copper plating and the bronze.

5. A bearing element comprising: a metal backing having a copper surface and a bearing lining of a tin-alloying metal bonded thereto, said backl0 ing and lining being integrally bonded together by an intervening strata whose entire thickness is`composed of an alloy of copper and tin having a relatively high melting point compared to that of pure tin. l5

6. A bearing element comprising: a metal backing and a bearing lining of tin-alloying metal, said backing and lining being integrally bonded together by a copper plating upon the contacting surface of said backing and a series of small areas of a bonding strata whose entire thickness having a higher copper content than obtains in CuaSn.

CHARLES R. SHORT. 25

ROLAND P. KOEHRING. 

